This invention relates to an apparatus for detecting defects on a bottle mouth with a screw thread and particularly to an apparatus capable of detecting defects on the entire periphery of a bottle mouth without rotating the bottle by forming concentric planar optical images of the bottle mouth.
Some of glass bottles for liquor or soft drink, newly manufactured or recovered from market for reuse, have flaws, scratches or cracks on their bottle mouths. These defects cause incompletely airtight sealing of a bottle mouth and sanitary problems with respect to liquor or soft drink thereafter sealed in the bottles. Accordingly, it is necessary to detect such defects on the mouths of these bottles to omit those bottles with defects.
Various methods of detecting defects on a bottle mouth have been proposed. In each method, however, the bottle is rotated through 360.degree. to detect the whole screw thread about the bottle mouth, and the image of the entire screw thread is formed through a linear senser or TV camera. The image of the screw thread is converted into electric signals to be processed.
In these conventional methods, therefore, a mechanism for rotating each bottle to be detected is indispensable and causes a complex structure, increases the number of structural members and raises the manufacturing cost. Further, as the entire part of a screw thread is detected during one rotation of each bottle, the entire part thereof cannot be detected instantly. Therefore, a great number of bottles cannot be detected in a short time.